Load transfer switch assembly

ABSTRACT

An electric circuit load center for recreational vehicles equipped with a load transfer switch assembly operable to connect a utility power supply to a load and separately operable to connect a generator power supply to the load. The load transfer switch assembly has a control member operable in response to movement of separate switch handles to insure that only one power supply is connected to the load at any one time.

United States Patent Nerem 5] Mar. 7, 1972 {54] LOAD TRANSFER SWITCHASSEMBLY FOREIGN PATENTS OR APPLICATIONS [72] Inventor: Marvin E. Nerem,136 East M. Street, 787,469 12/ 1957 Great Britain ..200/42 T FoiestCity, Iowa 50436 Primary Examiner-Robert K. Schaefer [22] 1970 AssistantExaminer-M. Ginsburg [21] Appl. No.: 89,957 Attorney-Burd, Braddock &Bartz [57] ABSTRACT [52] U.S.Cl. ..200/50C [51] Int. Cl. ..H01h 9/24elecmc load center recreatlonal vch'cles [58] Field of Search ..200/50c,5 R,5 A, 5 B, 5c, eFlipped with a switch assembly Warm)"3 200/5 D 5 E5 F 172 A 172 317/1 12420 connect a utility power supply to a load andseparately operable to connect a generator power supply to the load. Theload [56] References Cited transfer switch assembly has a control memberoperable in response to movement of separate switch handles to insureNITE ST TES EN S that only one power supply is connected to the load atany one time. 3,492,448 1/1970 Phillips ..220/50 C 805,057 11/1905 Craft..200/5 R X 9 Claims 4 Drawing Figures li 4A /0 E:T

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Patented March 7, 1972 3,647,997

2 Sheets-Sheet 2 2 OFF OFF 7 INVIZN'I'UR. MARVIN E. NEREM ATTORNEYS LOADTRANSFER SWITCH ASSEMBLY BACKGROUND OF INVENTION:

Many recreational vehicles as motor homes, truck campers, traveltrailers and the like, are equipped with electric generating units tosupply electric power to air conditioners, appliances and electriclights. The electrical wiring system of recreational vehicles includes apower connection or socket adapted to be connected to a conventionaloutside 110-volt power supply or utility power supply. The electricalwiring system also has a load transfer switch operable to disconnect thegenerator from the circuit when the utility power supply is connected tothe vehicle circuit. Manually operated load transfer switches are notdesigned to automatically disconnect the generator when the utilitypower supply is connected to the circuit. When both power supplies areconnected to the load the result is damage to the generator and thegenerator controls.

SUMMARY OF INVENTION The invention relates to a load transfer switchassembly operable to connect a first power source and a second powersource selectively and independently toa load. The switch assembly has acontrol means which allows only one power source at a time to beconnected to the load. The switch assembly has a pair of electricswitches having operating handles that are selectively movable to on and"off" positions. The switches can be electrical circuit breakers. Eachswitch is adapted to be connected to a separate power source so thatwhen the switch handle is in the on position the power source isconnected to the load. The control means comprises a movable memberengageable with the handles of the switches so that when one handle ofone switch is moved to the on position the handle of the other switch ismoved to the off position before the first switch is snapped on". Thisinsures the connection of only one power source at a time to the load.The control means has a slide member that is movably mounted on a blockattached to casings of the switches. The slide member has oppositetransverse edges which engage the operating handles of the switches sothat the switches must work together.

An object of the invention is to provide a low cost and safe loadtransfer switch assembly with a control means operable to insure thatonly one power source at a time is connected to a load. Another'objectof the invention is to provide a coordinated control structure forconventional circuit breakers that is usable with the circuit breakerswithout modifying the circuit breaker structure or casing.

IN THE DRAWINGS:

FIG. 1 is a front plan view of a switch panel equipped with the loadtransfer switch assembly of the invention;

FIG. 2 is a circuit diagram connecting the load transfer switch assemblyto an outside power supply, a generator and load center;

FIG. 3 is a top plan view of the load transfer switch assembly; and

FIG. 4 is a side view of the load transfer switch assembly taken alongline 4-4 of FIG. 3.

Referring to the drawing there shown in FIG. 1, a fragmenmy plan view ofthe top of a switch box or panel indicated generally at 10. The panelcomprises a box housing electrical switches as circuit breakers, of anelectrical system, as used in recreational vehicles. The load transferswitch assembly 12 can be used in any electrical system adapted toutilize separate power sources.

The panel 10 has a top coverof 11 extended over a load transfer switchassembly indicated generally at 12; The cover ll has aligned openings 13and 14 for accommodating the upper sides of the switch assembly.Removable elongated strips 16 and 17 located on opposite sides of theopenings 13 and 14 provide additional spaces to accommodate addedswitches, as circuit breakers. All of the circuit breakers can bemounted in the panel so that the entire load center for the electricalsystem is located in the panel 10. Alternatively, the load center can bein a separate switch box connected to the load transfer switch assembly.

Referring to FIG. 2, there is shown a circuit diagram which includes theload transfer switch assembly 12. Switch assembly 12 comprises a firstpair of circuit breakers 18 and 19 having operating handles 21 and 22coupled together with a link 23. Handles 21 and 22 are selectivelymovable together to off and on positions. Longitudinally aligned withthe first pair of circuit breakers l8 and 19 is a second pair of circuitbreakers 24 and 25. Projected upwardly from the one end of the circuitbreakers 24 and 25 are operating handles 26 and 27 coupled together witha link 28. Operating handles 26 and 27 are selectively movable to on andoff positions. The circuit breakers 18, 19, 24 and 25 are connected to acommon conductor 29 formed of two electrically insulated portions 29Aand 29B.

The first pair of circuit breakers 18 and 19 are connected to an outsidepower supply or utility volt power supply 31 through a socket orpolarized plug 32. Plug 32 is also connected to a ground bar 33 locatedin the switch box 10. Circuit breakers 24 and 25 are connected to theelectric generator 34. When the operating handles 26 and 27 are in theon position the generator 34 is electrically connected to the conductor29. The operating handles 21 and 22 are in the ofF position so that onlythe generator 34 is connected to the conductor 29. The outside powersupply remains disconnected from the conductor as long as the switches24 and 25 are on. The conductor 29 and ground bar 33 are connected withsuitable lines to load 36, as a coach load center. The load center canbe located within the panel 10 by the use of additional circuit breakerscoupled to the conductor 29 and a suitable bracket mounted on the baseof the panel.

Referring to FIG. 4, there is shown longitudinally aligned circuitbreakers 18 and 24 mounted in assembled relation with the switch controlmeans indicated generally at 37. The circuit breakers are identical instructure and operation. The following description is directed tocircuit breaker l8. Corresponding parts of circuit breaker 24 have thesame reference numbers with a suffix .A". Examples of suitable circuitbreakers are the General Electric type TQP, and the circuit breakersshown in U.S. Pat. Nos. 2,922,004 and 2,953,650. Circuit breaker 18 hasan electrically insulative casing or housing 38 having an outwardlydirected toe 39 at one end of the bottom of the casing. The toe 39engages a hook-shaped bracket 41 mounted on the base 42 of the panel 10.An electrical insulative block 43 is secured to the midportion of thebase 42. The electrical conductor 29 is mounted on the block 43. Theswitch 18 has a load terminal 44 that clamps on an upright bridge memberof the conductor 29. The top portion of the front face of the casing 38has an inwardly directed cavity or recess 46.

The front walls of the casings 38 and 38A are located in a face to faceengaging relationship thereby longitudinally aligning the operatinghandles 21 and 26. The circuit breakers l9 and 25 are identical instructure and are mounted in the same manner on the brackets 41' and 41Aand the conductor 29. In other words, the first pair of circuit breakersl8, 19 are longitudinally positioned with respect to the second pair ofcircuit breakers. The operating handles 21 and 22 move in the samegeneral longitudinal direction or plane as the operating handles 26, 27.

The control means 37 for the circuit breakers l8, l9 and 24, 25 has apair of sidewalls 48 and 49 located adjacent the outside faces of thecircuit breaker casings. The sidewalls 48 and 49 are connected with toptransverse walls 51 and 52 thereby form a one piece generally U-shapedunit that fits over the circuit breaker casings between the operatinghandles 21, 22 and 26, 27. The top wall 51 has an outside transverseedge 53 that is engageable with the operating handles 21 and 22. The topwall 52 has the outside transverse edge 54 that is engageable withoperating handles 26 and 27. The longitudinal distance between thetransverse edges 53 and 54 is such that the operating handles 21 and 22,26 and 27 can not both be in their on positions at the same time. Thisdistance is such that when the handles 21 and 22 are moved from the off"position to the on position, the handles 26 and 27, if they are in theiron position, are moved to the off position before the circuit breakersl8 and 19 are snapped on. The walls 51 and 52 are longitudinallyseparated from each other to provide space for the portion of the topcover between the operating handles 21, 22 and 26, 27.

The sidewalls 48 and 49 are slideably mounted on a transverse block 56located in the inwardly directed recesses 46 and 46A of the switchcasings 38 and 38A. The block 56 made of electrically insulated materialis secured with adhesive or similar material to the casings 38 and 38A.This prevents the control member 37 from separating from the circuitbreakers. The midportions of the sidewalls 48 and 49 have longitudinalslots 57 accommodating fasteners 58 and 59, as screws or bolts whichfunction to slideably guide the sidewalls for longitudinal movement onthe block 56 and mount the movable portion of the control means on theblock.

In use, the control means 37 functions to interrelate the on and offfunctions of the aligned switches l8, l9 and 24, 25. The first pair ofcircuit breakers 18 and 19 connected to the outside power supply areoperative to connect this power supply to the load 36. When this is donethe operating handles 21 and 22 are in their on" positions. The controlmember 37 forces the operating handles 26 and 27 to their off positionsthereby disconnecting the generator 34 from the electrical system. Thelongitudinal distance between the transverse edges 53 and 54 of thecontrol member 37 is such that the circuit breakers 24 and 25 aredisconnected from the circuit before the circuit breakers 18 and 19 aretripped on. The operating handles 26 and 27 are moved by the controlmember 37 past their overcenter positions toward their off" positionbefore the operating handles 21 and 22 move past the overcenterpositions toward their on positions. The same conditions occur onopposite movements of the handles 21, 22 and 26, 27. This eliminates anelectrical connection between the outside power supply and the generatoras only one power supply at one time is connected to the load.

When the generator 34 is connected to the load 36 the control means 37is operative to disconnect the outside power supply by tripping thecircuit breakers 18 and 19. This is accomplished by moving the first setof operating handles 21 and 22 to the ofF' position before the secondset of operating handles 26 and 27 are tripped to the on position. Asshown in the broken lines in FIG. 4, the entire U shaped clip comprisingthe sidewalls 48 and 49 and top walls 51 and 52 slide relative to theswitch casings, fasteners and guide 58 and 59 to control the switchingactions of the operating handles 21, 22 and 26, 27..Both sets of handles21, 22 and 26, 27 can be located in their off positions therebydisconnecting both power sources from the load 36.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A load transfer switch assembly operable to connect a first powersource and a second power source selectively and independently to a loadcomprising: a first switch means having a first operating memberselectively movable to on and off positions, said first switch meansadapted to be connected to the first power source and the load wherebywhen the first member is in the on" position, the first power source isconnected to the load, a second switch means generally longitudinallyaligned with said first switch means and having a second operatingmember selectively movable to on" and "off positions, said second switchmeans adapted to be connected to the second power source and the loadwhereby when the second member is in the on position, the second powersource is connected to the load, and longitudinally movable controlmeans comprised of a generally U-shaped unit, having a pair of sidewallsconnected with first and second top transverse walls, said toptransverse walls havi n respective first and second transverse edgesengageable W! the first member and the second member, respectively, andoperable to move the second member to its off position when the firstmember is moved to its on position and to move the first member to theoff position when the second member is moved to its on position, wherebyonly one power source at a time is connected to the load.

2. The switch assembly of claim 1 wherein: the first switch means andthe second switch means are circuit breakers having operating handles,said control means located between the operating handles of the circuitbreakers to control the relative positions of the operating handles.

3. The switch assembly of claim 2 including: means mounting the U-shapedunit for general longitudinal movement between the operating handles.

4. The switch assembly of claim 3 wherein: the mounting means comprisesa block mounted on the circuit breakers and guide means movablyconnecting the U-shaped unit with the block. 1

5. Theswitch assembly of claim 1 wherein: the first switch means and thesecond switch means each have an elongated casing, said Ushaped unitslideably positioned on the elongated casings of the switch meansbetween the operating members of the switch means.

6. The switch assembly of claim 5 including: means secured to at leastone casing for guiding the movement of the U- shaped unit.

7. The switch assembly of claim 1 wherein: the first switch means andthe second switch means are longitudinally aligned circuit breakershaving operating handles, said control means located between theoperating handles and slideably mounted on the circuit breakers.

8. The switch assembly of claim 1 wherein: the first switch meanscomprise a first pair of circuit breakers having operating handleslinked together, and the second switch means comprise a second pair ofcircuit breakers having operating handles linked together, said firstpair of circuit breakers being located in longitudinal alignment withthe second pair of circuit breakers, said control means having a movablemember engageable with at least one operating handle on each pair ofcircuit breakers.

9. The switch assembly of claim 8 including: block means mounted on thecircuit breakers and guide means mounting the movable means on the blockmeans.

1. A load transfer switch assembly operable to connect a first powersource and a second power source selectively and independently to a loadcomprising: a first switch means having a first operating memberselectively movable to ''''on'''' and ''''off'''' positions, said firstswitch means adapted to be connected to the first power source and theload whereby when the first member is in the ''''on'''' position, thefirst power source is connected to the load, a second switch meansgenerally longitudinally aligned with said first switch means and havinga second operating member selectively movable to ''''on'''' and''''off'''' positions, said second switch means adapted to be connectedto the second power source and the load whereby when the second memberis in the ''''on'''' position, the second power source is connected tothe load, and longitudinally movable control means comprised of agenerally Ushaped unit, having a pair of sidewalls connected with firstand second top transverse walls, said top transverse walls havingrespective first and second transverse edges engageable with the firstmember and the second member, respectively, and operable to move thesecond member to its ''''off'''' position when the first member is movedto its ''''on'''' position and to move the first member to the''''off'''' position when the second member is moved to its ''''on''''position, whereby only one power source at a time is connected to theload.
 2. The switch assembly of claim 1 wherein: the first switch meansand the second switch means are circuit breakers having operatinghandles, said control means located between the operating handles of thecircuit breakers to control the relative positions of the operatinghandles.
 3. The switch assembly of claim 2 including: means mounting theU-shaped unit for general longitudinal movement between the operatinghandles.
 4. The switch assembly of claim 3 wherein: the mounting meanscomprises a block mounted on the circuit breakers and guide meansmovably connecting the U-shaped unit with the block.
 5. The switchassembly of claim 1 wherein: the first switch means and the secondswitch means each have an elongated casing, said U-shaped unit slideablypositioned on the elongated casings of the switch means between theoperating members of the switch means.
 6. The switch assembly of claim 5including: means secured to at least one casing for guiding the movementof the U-shaped unit.
 7. The switch assembly of claim 1 wherein: thefirst switch means and the second switch means are longitudinallyaligned circuit breakers having operating handles, said control meanslocated between the operating handles and slideably mounted on thecircuit breakers.
 8. The switch assembly of claim 1 wherein: the firstswitch means comprise a first pair of circuit breakers having operatinghandles linked together, and the second switch means comprise a secondpair of circuit breakers having operating handles linked together, saidfirst pair of circuit breakers being located in longitudinal alignmentwith the second pair of circuit breakers, said control means having amovable member engageable with at least one operating handle on eachpair of circuit breakers.
 9. The switch assembly of claim 8 including:block means mounted on the circuit breakers and guide means mounting themovable means on the block means.